RAC学习笔记

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RAC简介

RAC要解决的问题是传统ios中事件，通知，回调的机制十分的繁琐。

常规用法

target-action

  • RAC可以替代一般的target-action操作，例如监测textField的文字的改变，不是用RAC的写法
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- (void)viewDidLoad {
    [super viewDidLoad];

    UITextField *text = ({
        UITextField *text = [[UITextField alloc] init];
        [self.view addSubview:text];
        [text mas_makeConstraints:^(MASConstraintMaker *make) {
            make.center.equalTo(self.view);
            make.size.mas_equalTo(CGSizeMake(200, 40));
        }];
        text.backgroundColor = [UIColor redColor];
        [text addTarget:self action:@selector(textDidChange:) forControlEvents:UIControlEventEditingChanged];
        text;
    });
}

- (void)textDidChange:(UITextField *)sender {
    NSLog(@"did change: %@", sender);
}
  • 使用RAC的写法：
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    - (void)viewDidLoad {
        [super viewDidLoad];

        UITextField *text = ({
            UITextField *text = [[UITextField alloc] init];
            [self.view addSubview:text];
            [text mas_makeConstraints:^(MASConstraintMaker *make) {
                make.center.equalTo(self.view);
                make.size.mas_equalTo(CGSizeMake(200, 40));
            }];
            text.backgroundColor = [UIColor redColor];

            [[text rac_signalForControlEvents:UIControlEventEditingChanged] subscribeNext:^(id x) {
                NSLog(@"%@", x);
            }];

            // 或者
            //[text.rac_textSignal subscribeNext:^(id x) {
            //    NSLog(@"%@", x);
            //}];

            text;
        });
    }

手势中使用RAC

  • RAC可以替换手势的方法，代码如下
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- (void)viewDidLoad {
    [super viewDidLoad];

    self.view.userInteractionEnabled = YES;
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] init];
    [[tap rac_gestureSignal] subscribeNext:^(id x) {
        NSLog(@"%@", x);
    }];
    [self.view addGestureRecognizer:tap];
}

通知

  • RAC可以代替通知，并且RAC的通知不用移出
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- (void)viewDidLoad {
    [super viewDidLoad];
    [[[NSNotificationCenter defaultCenter] rac_addObserverForName:UIApplicationDidBecomeActiveNotification object:nil] subscribeNext:^(id x) {
        NSLog(@"%@", x);
    }];
}

定制器

  • RAC可以代替定时器
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- (void)viewDidLoad {
    [super viewDidLoad];

    // 延迟2秒执行
    [[RACScheduler mainThreadScheduler] afterDelay:2.0 schedule:^{
        NSLog(@"haha");
    }];

    // interval为间隔事件，scheduler为在那个线程上执行，leeway为多久之后开始执行。
    [[RACSignal interval:2.0 onScheduler:[RACScheduler mainThreadScheduler] withLeeway:5.0] subscribeNext:^(NSDate x) {
        NSLog(@"%@", x);
    }];

}

代理

  • RAC可以替换代理，但仅限没有返回值的代理
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@interface ViewController ()<UITableViewDelegate>
@property (nonatomic, strong) UIAlertView *alertView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.alertView = [[UIAlertView alloc] initWithTitle:@"RAC" message:@"test" delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
    [[self rac_signalForSelector:@selector(alertView:clickedButtonAtIndex:) fromProtocol:@protocol(UIAlertViewDelegate)]subscribeNext:^(id x) {
        NSLog(@"%@",x);
    }];
    // 或者
    // [[self.alertView rac_buttonClickedSignal] subscribeNext:^(id x) {
    //     NSLog(@"%@", x);
    // }];

    [self.alertView show];
}

@end

KVO

  • RAC可以替换KVO
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@interface ViewController ()

@property (nonatomic, assign) NSInteger index;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    [RACObserve(self, index) subscribeNext:^(id x) {
        NSLog(@"%@", x);
    }];

}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    self.index++;
}

@end

高级用法

创建信号

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- (void)viewDidLoad {
    [super viewDidLoad];

    RACSignal *signal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        NSURLRequest *req = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com"]];
        [NSURLConnection sendAsynchronousRequest:req queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {
            if (connectionError) {
                // 请求失败
                [subscriber sendError:connectionError];
            }
            else {
                // 请求成功
                [subscriber sendNext:data];
            }
            [subscriber sendCompleted];
        }];
        return [RACDisposable disposableWithBlock:^{
            // 取消订阅
            NSLog(@"cancel");
        }];
    }];

    RACDisposable *disposable = [signal subscribeNext:^(NSData *responseData) {
        NSLog(@"%@", responseData);
    } error:^(NSError *error) {
        NSLog(@"%@", error);
    } completed:^{
        NSLog(@"completed");
    }];

    // 订阅完就取消订阅，这样就不会执行订阅block了
    [disposable dispose];
}

信号处理

  • map:映射
  • filter:过滤
  • delay:延时
  • startWith:在接收到信号前，先接收到一个信号
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- (void)viewDidLoad {
    [super viewDidLoad];

    UITextField *textField = ({
        UITextField *view = [[UITextField alloc] init];
        [self.view addSubview:view];
        [view mas_makeConstraints:^(MASConstraintMaker *make) {
            make.center.equalTo(self.view);
            make.size.mas_equalTo(CGSizeMake(200, 40));
        }];
        view.backgroundColor = [UIColor redColor];
        view;
    });

    [[[[[[textField rac_textSignal] map:^id(id value) {
        NSString *str = (NSString *)value;
        return @([str length]);
    }] filter:^BOOL(id value) {
        return [value integerValue] > 3;
    }] delay:2] startWith:@"haha"] subscribeNext:^(id x) {
        NSLog(@"%@", x);
    }];
}
  • timeout:超时
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RACSignal *signal = [[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {

    [[RACScheduler mainThreadScheduler] afterDelay:1.0 schedule:^{
        [subscriber sendNext:@"hello"];
        [subscriber sendCompleted];
    }];
    return nil;

}] timeout:2.0 onScheduler:[RACScheduler mainThreadScheduler]]; // 如果请求没有在2秒内完成，则请求超时，会调用errorBlock

[signal subscribeNext:^(NSData *responseData) {
    NSLog(@"%@", responseData);
} error:^(NSError *error) {
    NSLog(@"%@", error);
} completed:^{
    NSLog(@"completed");
}];
  • take:接收到多次信号，但只处理前几次信号
  • takeLast:只处理最后几次信号
  • skip:忽略几次
  • takeUntilBlock:返回YES可以表示不接收，返回NO表示接收该信号，与filter类似
  • takeWhileBlock:当返回一次YES后，就停止接收所有信号
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RACSignal *signal = [[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {

    [subscriber sendNext:@"hello1"];
    [subscriber sendNext:@"hello2"];
    [subscriber sendNext:@"hello3"];
    [subscriber sendNext:@"hello4"];
    [subscriber sendNext:@"hello5"];
    [subscriber sendCompleted];
    return nil;

}] takeLast:2];

[signal subscribeNext:^(id value) {
    NSLog(@"%@", value);
}];
  • throttle:节流，可以规定两个信号的间隔时间必须大于某个值
  • distinctUntilChanged:直到订阅的内容发生变化才会处理信号
  • ignore:忽略某些信号值
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UITextField *textField = ({
    UITextField *view = [[UITextField alloc] init];
    [self.view addSubview:view];
    [view mas_makeConstraints:^(MASConstraintMaker *make) {
        make.center.equalTo(self.view);
        make.size.mas_equalTo(CGSizeMake(200, 40));
    }];
    view.backgroundColor = [UIColor redColor];
    view;
});

// 如果文字的改变速度过快，则不处理，两次信号间隔时间必须大于0.3秒
[[[[[textField rac_textSignal] throttle:0.3] distinctUntilChanged] ignore:@""] subscribeNext:^(id x) {
    NSLog(@"%@", x);
}];
  • flattenMap:订阅的值为一个信号，将该信号转为订阅具体的值
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UITextField *textField = ({
    UITextField *view = [[UITextField alloc] init];
    [self.view addSubview:view];
    [view mas_makeConstraints:^(MASConstraintMaker *make) {
        make.center.equalTo(self.view);
        make.size.mas_equalTo(CGSizeMake(200, 40));
    }];
    view.backgroundColor = [UIColor redColor];
    view;
});

[[[textField.rac_textSignal throttle:0.3] flattenMap:^id(id value) {
    return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        [subscriber sendNext:@"aaa"];
        [subscriber sendCompleted];
        return [RACDisposable disposableWithBlock:^{

        }];
    }];
}] subscribeNext:^(id x) {
    NSLog(@"%@", x);
}];
  • repeat:重复发送某个信号
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RACSignal *signal = [[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        [subscriber sendNext:[NSDate date]];
        [subscriber sendCompleted];
        return nil;
    }] repeat];

    [signal subscribeNext:^(id x) {
        NSLog(@"%@", x);
    }];
  • merge:同时订阅两个信号源，无论哪个发出信号，都会执行
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RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
      dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
          [subscriber sendNext:@"1"];
          [subscriber sendCompleted];
      });
      return nil;
  }];

  RACSignal *signalB = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
      dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
          [subscriber sendNext:@"2"];
          [subscriber sendCompleted];
      });
      return nil;
  }];

  [[signalA merge:signalB] subscribeNext:^(id x) {
      NSLog(@"%@", x);
  }];
  • combineLatest:reduce:这是一个RACSignal的类方法，表示同时聚合多个信号
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RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [subscriber sendNext:@"1"];
            [subscriber sendCompleted];
        });
        return nil;
    }];

    RACSignal *signalB = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            [subscriber sendNext:@"2"];
            [subscriber sendCompleted];
        });
        return nil;
    }];

    [[RACSignal combineLatest:@[signalA, signalB] reduce:^id(NSString *s1, NSString *s2){
        NSLog(@"s1=%@, s2=%@", s1, s2);
        return [NSString stringWithFormat:@"%@%@", s1, s2];
    }] subscribeNext:^(id x) {
        NSLog(@"%@", x);
    }];
  • concat:先订阅信号A，A执行完成后再订阅信号B
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RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [subscriber sendNext:@"1"];
        [subscriber sendCompleted];
    });
    return nil;
}];

RACSignal *signalB = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [subscriber sendNext:@"2"];
        [subscriber sendCompleted];
    });
    return nil;
}];

// 先订阅A，A执行完成后，再执行B，如果A失败了，不会再执行B
[[signalA concat:signalB] subscribeNext:^(id x) {
    NSLog(@"%@", x);
}];
  • zipWith:两个信号都发出后，再执行，也可以使用combineLatest:
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RACSignal *signalA = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [subscriber sendNext:@"1"];
        [subscriber sendCompleted];
    });
    return nil;
}];

RACSignal *signalB = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [subscriber sendNext:@"2"];
        [subscriber sendCompleted];
    });
    return nil;
}];

[[signalA zipWith:signalB] subscribeNext:^(id x) {
    // x是一个RACTuple，包含了signalA和signalB的值
    NSLog(@"%@", x);
}];

RAC的坑

  • side effect: 一个信号源被多个订阅者订阅，每个订阅者收到的信号可能不一样。解决方法：使用reply
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RACSignal *signalA = [[RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
    static int i = 0;
    i++;
    [subscriber sendNext:@(i)];
    [subscriber sendCompleted];
    return nil;
}] replay];

[signalA subscribeNext:^(id x) {
    NSLog(@"%@", x);
}];

[signalA subscribeNext:^(id x) {
    NSLog(@"%@", x);
}];